It is
estimated that there are between 300 and 400
species in this genus depending on the
taxonomist consulted. They are native to
Europe,
Asia,
Africa and North America. The
genus name comes from the Greek for "an ear of
grain" and refers to the
inflorescence form.

* Guides and Keys are from the book
"Herbaceous Perennial Plants A Treatise on their Identification,
Culture and Garden Attributes" by
Dr
Allan M. Armitage of the University of Georgia. Varsity Press,
Athens, Georgia. 1989 ISBN 0-942375-00.
More on Dr
Armitage and his other books.